The present invention relates to low-crystalline polymer films and laminates thereof. Such materials have a wide variety of uses, especially in the areas of limited use or disposable items.
Elastomeric films have been traditionally used to provide barrier properties in limited use or disposable items. The terms "limited use" and "disposable" mean that the product or component is used only once, or only a small number of times, before being discarded. Examples of such products include, but are not limited to, surgical and health care related products such as hospital drapes and gowns, disposable work wear such as coveralls and lab coats and personal care absorbent articles such as diapers, training pants, incontinence products, sanitary napkins, bandages, wipes and the like. In the area of protective apparel, films are used to prevent cross-exchange of microorganisms between the patient and the wearer. Films are used as the outer covers in personal care absorbent articles to prevent body wastes from contaminating the clothing, bedding and other aspects of the surrounding environment.
Lamination of films has been used to create materials that are impervious. Surgical gowns and the outer covers of premium-priced diapers are some examples. A primary purpose of the film in such laminations is to provide barrier properties. The laminates must also be tough, i.e., have high tensile strength in both the machine direction and the cross machine direction, for durability.
Traditionally, elastomeric films are made from linear polymers such as polyurethanes, linear low density polyethylenes made with metallocene catalysts which are available from The Dow Chemical Company of Midland, Mich. and Exxon Corporation of Houston, Tex., Catalloys which are available from Montell USA of Wilmington, Del. and KRATON.RTM. brand polymers which are available from Shell Chemical Company of Houston, Tex. One problem with such linear polymers is that while they provide high tensile strength in the machine direction, the resulting film is weak in the cross machine direction when machine-direction oriented. Thus, the film is not tough and breaks easily. Another problem with traditional linear polymers is that they generally contain high levels of ethylene, and ethylene, while promoting softness, weakens tensile strength. When tensile strength is weak, it takes less force to break the film. In order to prevent breakage, the film must be of a higher gauge, which means a higher cost of manufacture.
A need exists, therefore, for inexpensive elastomeric films that are strong in both the machine direction and the cross machine direction, as well as a process of making the same.